Ricerc@Sapienza

One of the major limits of chemotherapy is depending on the ability of the cancer cells
to elude and adapt to dierent drugs. Recently, we demonstrated how the activation of the M2
muscarinic receptor could impair neuroblastoma cell proliferation. In the present paper, we investigate
the possible eects mediated by the preferential M2 receptor agonist arecaidine propargyl ester (APE)
on drug resistance in two neuroblastoma cell lines, SK-N-BE and SK-N-BE(2C), a sub-clone presenting
drug resistance. In both cell lines, we compare the expression of the M2 receptor and the eects
mediated by the M2 agonist APE on cell cycle, demonstrating a decreased percentage of cells in S
phase and an accumulation of SK-N-BE cells in G1 phase, while the APE treatment of SK-N-BE(2C)
cells induced a block in G2/M phase. The withdrawal of the M2 agonist from the medium shows
that only the SK-N-BE(2C) cells are able to rescue cell proliferation. Further, we demonstrate that
the co-treatment of low doses of APE with doxorubicin or cisplatin significantly counteracts cell
proliferation when compared with the single treatment. Analysis of the expression of ATP-binding
cassette (ABC) eux pumps demonstrates the ability of the M2 agonist to downregulate their
expression and that this negative modulation may be dependent on N-MYC decreased expression
induced by theM2agonist. Our data demonstrate that the combined eect of low doses of conventional
drugs and the M2 agonist may represent a new promising therapeutic approach in neuroblastoma
treatment, in light of its significant impact on drug resistance and the possible reduction in the side
eects caused by high doses of chemotherapy drugs.